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Spinning information for better memory

With the ever-decreasing scale of electronics, quantum physicists say it is crucial to find new approaches for making this happen. "As consumers want more powerful technology, we need to find new ways to supply this demand" says the University of Sydney's Dane McCamey.

One leading approach is "spintronics", where the magnetic character, or spin, of electrons and even nuclei are used to store information. Scientists have now shown that the spin of atomic nuclei in silicon can store information for over a minute and that the information can then be read out electrically, an important step in linking spintronics with classical electronics.

The research is published in the journal Science by an international team comprising Dane McCamey, Hans van Tol, Gavin Morley and Christoph Boehme.

The experiments are the first to controllably flip the state of nuclear spins in silicon between a "0" and a "1" and then read out the effect this has on an electric current. Unique equipment for controlling electronic and nuclear spins in high magnetic fields and at very low temperatures made this possible at the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, Florida.

"Our use of silicon makes these findings particularly exciting for semiconductor companies, who are experts in silicon" the lead author, Dane McCamey (Universities of Sydney and Utah) commented. "Because the nuclear spins are better isolated from their environment than electronic spins, they can store information for longer" added Christoph Boehme, from the University of Utah.

"The high magnetic fields we use enable the electron spins to be lined up, initializing them so they are ready to store information" pointed out Hans van Tol, of the NHMFL "We also show that we can line up the nuclear spins too".

"Electrical detection of electron spins is also the leading approach for detecting quantum information in silicon" said Gavin Morley (University College London and London Centre for Nanotechnology). "Future experiments could use this method to study quantum information stored in nuclear spins".
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This work was supported by the Australian Research Council, the UK Royal Commission for the Exhibition of 1851, the UK EPSRC COMPASSS grant, the US National Science Foundation and the National High Magnetic Field Laboratory (NHMFL). The NHMFL is funded by the State of Florida, the US Department of Energy, and the US National Science Foundation.

Electrons (green arrows) flow through a silicon chip and some are trapped by phosphorus atoms (blue arrows). A phosphorus atom can only capture a second electron if the two electrons have opposite spin, and this leads to a decrease in the electric current. This spin-trap was used to electrically read out the nuclear spin (red arrow), where information was stored for over 100 seconds. Animated image by Gavin W Morley.